1. Field the Invention
This invention relates to an ion-selective electrode for measuring carbonate concentration and an ion-selective electrodes pair for measuring carbonate concentration in an aqueous liquid sample. More particularly, this invention relates to an ion-selective electrode for measuring carbonate concentration and an ion selective electrodes pair for measuring carbonate concentration useful for clinical assay where aqueous liquid sample, particularly biological body fluid such as blood, lymph, saliva or urine is measured.
2. Description of the Prior Art
In order to maintain the pH of various biological body fluid represented by blood, there are physicochemical buffer system and physiological buffer system by lung and kidney in living body, and among them, bicarbonate or hydrogencarbonate buffer system of blood plasma is the most important.
As an ion-selective electrode for measuring total carbonate (carbonate ion) concentration potentiometrically, an ion-selective electrode for the analysis of carbonate concentration in liquid is disclosed in U.S. Pat. No. 4,272,328. The ion-selective electrode is composed of a reference electrode comprised of a conductive metal layer and a metal halide layer laminated thereon, an electrolyte layer, an ion-selective membrane zone or layer containing an ion carrier or an ionophore, and a buffer layer laminated in this order. This ion-selective electrode is resistant to the interference by salicylate, p-aminosalicylate, gentisate and the like, and measuring error is little. However, since the electrolyte layer contains hydrophilic polymer binder, this layer is liable to be separated from the ion-selective layer composed of hydrophobic organic material because of insufficient adhesive strength. Moreover, the strength of the ion selective layer is also insufficient. In addition, since the electrolyte layer containing hydrophilic polymer binder is subject to absorb moisture, and the stability of the electrode itself becomes worse in the course of time.